1. Field of the Invention
The present invention relates to a cleaning device for an image forming apparatus such as an electrostatic copying machine or an electrostatic printer using an electrophotographic process and an image forming apparatus using the cleaning device.
2. Description of the Related Art
It is difficult to transfer all of the toner of a toner image formed on a surface of an image bearing member to a transferring material during transferring in an image forming apparatus, and a slight amount of toner is not prevented from remaining on the image bearing member. Also, a transferring material dust or the like which is generated when the transferring material is in contact with the image bearing member is adhered to the image bearing member. For that reason, it is necessary that the image bearing member is sufficiently cleaned to remove the toner or the transferring material dust (hereinafter they are referred to as non-transferred toner) remaining on the image bearing member even after the toner image has been transferred onto the transferring material every time the transferring operation is made.
From the above viewpoint, there have been proposed various cleaning devices up to now. Among them, a cleaning device in which an edge of a cleaning blade made of an elastic material such as rubber is abutted against the image bearing member to scrape off the non-transferred toner so that the non-transferred toner is removed is simple in the structure, low in the cost and excellent in the non-transferred toner removing function. Therefore, the cleaning device of this type has been widely put in practical use.
FIG. 5 shows the structure of a conventional cleaning device which is disposed in proximity to a rotary cylindrical image bearing member 2. The image bearing member 2 has an axial line in a direction perpendicular to a paper surface of FIG. 5, and a charger, a developing device, a transfer means and the like (not shown) are disposed in the periphery of the image bearing member 2.
The cleaning device includes a casing 14 provided with an opening portion in the direction of the image bearing member 2, and the opening portion of the casing 14 is attached with a cleaning blade 15 made of urethane rubber or the like, and an edge of a distal end of the cleaning blade 15 is abutted against the image bearing member 2.
The non-transferred toner produced at a transfer position (not shown) is scraped off by the edge of the cleaning blade 15 to clean the surface of the image bearing member 2.
Also, because the non-transferred toner that has been scraped off by the cleaning blade 15 and remains there is again supplied to the edge of the cleaning blade 15 due to the rotation of the image bearing member 2 and then interposed between the image bearing member 2 and the cleaning blade 15, the frictional force of the cleaning blade 15 is lessened, thereby being capable of obtaining a stable cleaning performance without turning up the cleaning blade 15 or the like.
Incidentally, in recent years, an intention has been made to make the particle diameter of the toner smaller and to make the fusing speed of the toner higher for the purposes of higher image quality and higher process speed. It is difficult to remove the toner of this type from the image bearing member 2, resulting in such a problem that the toner fusion band is liable to occur.
Because the non-transferred toner deteriorates the frictional force of the cleaning blade at an abutting portion (abutting nip) of the cleaning blade against the image bearing member, and, at the same time, the non-transferred toner is pressed against the image bearing member by the cleaning blade, there is a case in which the fusion bond of the toner onto the image bearing member surface occurs. Japanese Patent Application Laid-open No. 9-218625 discloses the structure in which in order to eliminate the fusion bond of the toner, the viscosity component of the viscoelasticity characteristics of the rubber material that forms the cleaning blade is increased to suppress the vibration of the cleaning blade during sliding, thereby preventing the fusion bond of the toner onto the image bearing member. More specifically, the peak temperature of tanxcex4 obtained by the dynamic viscoelasticity test of a single-layer rubber that forms the blade is set to a value close to the photosensitive drum surface temperature.
However, in a method of increasing the viscosity component of the viscoelasticity characteristic of the single layer cleaning blade in order to prevent the fusion bond of the toner onto the image bearing member from occurring as in this structure, the deformation following property of the cleaning blade naturally obtained due to the elastic property and the force of restitution of the deformed cleaning blade become small. For that reason, with respect to the small particle diameter toner, if the viscosity component of the cleaning blade is too large for the purpose of suppressing the vibration of the blade during sliding, the cleaning performance against the non-transferred toner is degraded due to the shortage of the deformation-following property of the cleaning blade and the shortage of the force of restitution of the deformed cleaning blade, and the toner is liable to enter the interior of the nip between the cleaning blade and the image bearing member, resulting in such a problem that the toner fusion bond occurs.
Also, Japanese Patent Application Laid-open No. 56-55979 discloses a structure in which the cleaning blade is formed of an elastic rubber base and a hard synthetic resin layer to abut the hard resin layer against the image bearing member for the purpose of improving the abrasion resistance, the lubricity and the cleaning property of the cleaning blade.
However, in this structure, because the abutting portion of the cleaning blade against the image bearing member is made of a hard resin, an elastic property is very short, as a result of which there arises such a problem that the uniform abutment of the cleaning blade against the image bearing member in the longitudinal direction is difficult, a partial clearance is liable to occur, thereby being liable to cause cleaning failure.
Also, Japanese Patent Application Laid-open No. 63-159892 discloses a structure in which, in a cleaning blade formed of two layers, a rubber layer of a support portion is lower in the peak temperature of tanxcex4 obtained by the dynamic viscoelasticity test than a rubber layer of the abutting portion against the image bearing member.
However, in the disclosure of the above publication, because the tanxcex4 peak temperature of the rubber layer of the support portion against the image bearing member is very low to xe2x88x9240 to xe2x88x9220xc2x0 C., the elastic property becomes strong when using the cleaning blade at a normal temperature with the result that the vibration of the cleaning blade is liable to occur during sliding, to thereby lead to the toner fusion bond.
The present invention has been made under the above-mentioned circumstances, and therefore an object of the present invention is to provide a cleaning device which is capable of preventing the fusion bond of the toner on the image bearing member while maintaining a high cleaning performance, and an image forming apparatus using the cleaning device.
In order to achieve the above object, according to the present invention, there is provided a cleaning device having a cleaning blade which is abutted against an image bearing member that bears an image and cleans the surface of the image bearing member, the cleaning blade comprising:
at least a first rubber layer which is abutted against the image bearing member;
and a second rubber layer that supports the first rubber layer;
wherein the tanxcex4 peak temperature obtained by a dynamic viscoelasticity test of the first rubber layer is a value close to the surface temperature of the image bearing member;
the tanxcex4 peak temperature obtained by a dynamic viscoelasticity test of the second rubber layer is lower than the tanxcex4 peak temperature of the first rubber layer.
According to the present invention, because the tanxcex4 peak temperature obtained by a dynamic viscoelasticity test of the first rubber layer is the value close to the surface temperature of the image bearing member, the cleaning blade can be used in a state where the rate of the viscosity component is the highest, and the stick-slip motion of the blade can be effectively suppressed, thereby being capable of preventing the fusion bond of the toner onto the image bearing member. In addition, because the tanxcex4 peak temperature obtained by a dynamic viscoelasticity test of the second rubber layer is set to be lower than the tanxcex4 peak temperature of the first rubber layer, the rate of the elasticity component of the second rubber layer becomes high, whereby the cleaning blade ensures the higher following property to maintain the higher cleaning performance.